U.S. patent number 7,563,527 [Application Number 10/553,692] was granted by the patent office on 2009-07-21 for fuel cell-atmospheric-pressure turbine hybrid system.
This patent grant is currently assigned to Kawasaki Jukogyo Kabushiki Kaisha. Invention is credited to Eiichi Harada, Junichi Kitajima, Takatoshi Shoji, Kazuo Tanaka, Seiji Yamashita.
United States Patent |
7,563,527 |
Tanaka , et al. |
July 21, 2009 |
Fuel cell-atmospheric-pressure turbine hybrid system
Abstract
A fuel cell-atmospheric-pressure turbine hybrid system uses the
thermal energy of a cell exhaust gas discharged from an
atmospheric-pressure, high-temperature fuel cell effectively, does
not need any additional emergency protective device, and enables
the use of lightweight, easy-to-process structural and piping
materials to reduces the cost. The fuel cell-atmospheric-pressure
turbine hybrid system includes: a combustor 2 for burning an
exhaust gas G1 discharged from an atmospheric-pressure,
high-temperature fuel cell 1; a turbine 3 in which a combustion gas
G2 discharged from the combustor 2 expands and the pressure of the
combustion gas G2 drops to a negative pressure; a compressor 4 for
compressing an exhaust gas G3 discharged from the turbine 3 to
increase the pressure of the exhaust gas G3; and a heat exchanger 5
for transferring heat from the high-temperature exhaust gas G3
discharged from the turbine 3 to low-temperature air A to be
supplied to the fuel cell 1.
Inventors: |
Tanaka; Kazuo (Kobe,
JP), Harada; Eiichi (Kakogawa, JP), Shoji;
Takatoshi (Kobe, JP), Kitajima; Junichi (Akashi,
JP), Yamashita; Seiji (Kobe, JP) |
Assignee: |
Kawasaki Jukogyo Kabushiki
Kaisha (Kobe-shi, JP)
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Family
ID: |
33554485 |
Appl.
No.: |
10/553,692 |
Filed: |
June 29, 2004 |
PCT
Filed: |
June 29, 2004 |
PCT No.: |
PCT/JP2004/009130 |
371(c)(1),(2),(4) Date: |
October 18, 2005 |
PCT
Pub. No.: |
WO2005/001974 |
PCT
Pub. Date: |
January 06, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060222919 A1 |
Oct 5, 2006 |
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Foreign Application Priority Data
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Jun 30, 2003 [JP] |
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2003-186933 |
Mar 5, 2004 [JP] |
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2004-062096 |
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Current U.S.
Class: |
429/415 |
Current CPC
Class: |
H01M
8/04022 (20130101); F02C 6/00 (20130101); Y02E
60/50 (20130101); H01M 16/00 (20130101); H01M
8/0662 (20130101); F05D 2220/60 (20130101) |
Current International
Class: |
H01M
8/04 (20060101) |
Field of
Search: |
;429/12,13,22,23,24,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A-0 400 701 |
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Dec 1990 |
|
EP |
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A-61-128471 |
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Jun 1986 |
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JP |
|
A-63-119163 |
|
May 1988 |
|
JP |
|
A-63-216270 |
|
Sep 1988 |
|
JP |
|
A-08-045523 |
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Feb 1996 |
|
JP |
|
A-10-012255 |
|
Jan 1998 |
|
JP |
|
A-2000-228208 |
|
Aug 2000 |
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JP |
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A-2002-188438 |
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Jul 2002 |
|
JP |
|
A-2003-193865 |
|
Jul 2003 |
|
JP |
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A-2003-288907 |
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Oct 2003 |
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JP |
|
Primary Examiner: Ryan; Patrick
Assistant Examiner: Wills; Monique
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
The invention claimed is:
1. A fuel cell-atmospheric-pressure turbine hybrid system
comprising: a combustor configured to burn a cell exhaust gas
discharged from an atmospheric-pressure, high-temperature fuel
cell, the atmospheric-pressure, high-temperature fuel cell to which
an atmospheric pressure air and an atmospheric pressure fuel are
supplied at an atmospheric pressure and from which the cell exhaust
gas is discharged at the atmospheric pressure; a turbine in which a
combustion gas discharged at the atmospheric pressure from the
combustor expands and the pressure of the combustion gas drops to a
negative pressure lower than the atmospheric pressure, the turbine
being configured to discharge a turbine exhaust gas at the negative
pressure; a compressor configured to compress the turbine exhaust
gas discharged from the turbine to increase the pressure of the
turbine exhaust gas to the atmospheric pressure and to discharge a
compressor exhaust gas at the atmospheric pressure; and a heat
exchanger configured to transfer heat from the turbine temperature
exhaust gas discharged from the turbine to the atmospheric pressure
air to be supplied to the fuel cell; an evaporator capable of
recovering heat from the turbine exhaust gas discharged from the
turbine and generating steam by the recovered heat; and a reforming
device configured to reform the atmospheric pressure fuel by using
steam generated by the evaporator and to supply the reformed fuel
to the fuel cell.
2. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 1, wherein the compressor exhaust gas discharged
from the compressor is mixed in the atmospheric pressure air to be
supplied to the fuel cell.
3. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 1 further comprising a cooling device disposed
below the heat exchanger and configured to cool the turbine exhaust
gas discharged from the heat exchanger.
4. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 3, wherein the compressor comprises a first
compressor and a second compressor disposed coaxially with the
first compressor, and the system further comprises a second cooling
device disposed between the first compressor and the second
compressor, the first compressor being configured to compress the
turbine exhaust gas discharged from the turbine to increase the
pressure of the turbine exhaust gas and to discharge a first
compressor exhaust gas, the second cooling device being configured
to cool the first compressor exhaust gas discharged from the first
compressor, the second compressor being configured to compress the
first compressor exhaust gas from the second cooling device to
increase the pressure of the first compressor exhaust gas and to
discharge the second compressor exhaust gas at the atmospheric
pressure as the compressor exhaust gas.
5. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 1 wherein an air intake branch line through
which part of the atmospheric pressure air to be supplied to the
fuel cell is supplied to the combustor.
6. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 1 further comprising a fuel supply device
configured to supply a fuel other than the cell exhaust gas to the
combustor.
7. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 1, wherein the combustor has a first combustor
and a second combustor, the first combustor being configured to
burn the cell exhaust gas discharged from the atmospheric-pressure,
high-temperature fuel cell and to discharge the combustion gas at
the atmospheric pressure, the turbine has a first turbine and a
second turbine disposed coaxially with the first turbine, in the
second turbine the combustion gas discharged from the first
combustor expands and the pressure of the combustion gas drops to a
first negative pressure lower than the atmospheric pressure, the
second combustor being capable of burning a fuel and the exhaust
gas discharged from the second turbine and being configured to
discharge a second combustion gas to the first turbine, the first
turbine in which the second combustion gas discharged from the
second combustion expands and the pressure of the second combustion
gas drops to the negative pressure, the first turbine being
configured to discharge the turbine exhaust gas at the negative
pressure, the compressor compresses the turbine exhaust gas
discharged from the first turbine to increase the pressure of the
turbine exhaust gas to the atmospheric pressure.
8. A fuel cell-atmospheric-pressure turbine hybrid system
comprising: a combustor configured to bum a cell exhaust gas
discharged from an atmospheric-pressure, high-temperature fuel
cell, the atmospheric-pressure, high-temperature fuel cell to which
an atmospheric pressure air and an atmospheric pressure fuel are
supplied at an atmospheric pressure and from which the cell exhaust
gas is discharged at the atmospheric pressure; a turbine in which a
combustion gas of a pressure substantially equal to the atmospheric
pressure discharged from the combustor expands and the pressure of
the combustion gas drops to a negative pressure lower than the
atmospheric pressure, the turbine being configured to discharge a
turbine exhaust gas at the negative pressure; a compressor
configured to compress the turbine exhaust gas discharged from the
turbine to increase the pressure of the turbine exhaust gas to the
atmospheric pressure and to discharge a compressor exhaust gas at
the atmospheric pressure; an air supply line through which air at
the atmospheric pressure is supplied to the combustor; an
evaporator capable of recovering heat from the turbine exhaust gas
discharged from the turbine and generating steam by the recovered
heat, and a reforming device configured to reform the atmospheric
pressure fuel by using steam generated by the evaporator and to
supply the reformed fuel to the fuel cell.
9. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 8 further comprising a heat exchanger configured
to transfer heat of the turbine exhaust gas discharged from the
turbine to the compressor exhaust gas discharged from the
compressor.
10. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 8 further comprising an air supply branch line
branched from the air supply line and configured to supply part of
air flowing through the air supply line to the fuel cell.
11. The fuel cell-atmospheric-pressure turbine hybrid system
according to claim 10 further comprising an air distribution valve
placed at the joint of the air supply line and the air supply
branch line and configured to adjust the distribution of air to the
air supply line and the air supply branch line.
Description
TECHNICAL FIELD
The present invention relates to a fuel cell-atmospheric-pressure
turbine hybrid system built by combining an atmospheric-pressure,
high-temperature fuel cell and an atmospheric-pressure turbine and
capable of efficiently generating electric power.
BACKGROUND ART
Each of known hybrid systems of this kind disclosed in Patent
documents 1 and 2 includes a combination of a high-pressure fuel
cell and a gas turbine for driving a generator.
Patent document 1: JP 8-45523 A (FIG. 1 and the specification)
Patent document 2: JP 10-12255 A (FIG. 1 and the specification)
The conventional hybrid system using a gas turbine combined with a
compressor, and a high-pressure fuel cell that operates at a high
pressure equal to or higher than the output pressure of the
compressor has the following problems. A small hybrid system has a
small gas turbine, and a fuel cell contained in a high-temperature,
high-pressure container. Therefore, the hybrid system needs a
protective device capable of properly carrying out a shutdown
procedure and of discharging a high-temperature, high-pressure gas
outside the system in an emergency. The protective device imposes a
large cost load on the small hybrid system. The hybrid system needs
a differential pressure control system and control techniques for
limiting the variation of differential pressure during emergency
shutdown within an allowable range determined on the basis of the
structural strength of the fuel cell. The differential pressure
control system also increases the cost of the hybrid system. The
high-temperature, high-pressure container and the high-temperature,
high-pressure pipes also increases the cost of the hybrid
system.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the present invention to provide a
fuel cell-atmospheric-pressure turbine hybrid system built by
combining an atmospheric-pressure, high-temperature fuel cell and
an atmospheric-pressure turbine, capable of effectively using the
thermal energy of the exhaust gas discharged from the
high-temperature fuel cell, not additionally needing an emergency
protection device and having simple construction.
A fuel cell-atmospheric-pressure turbine hybrid system includes: a
combustor for burning an exhaust gas discharged from an
atmospheric-pressure, high-temperature fuel cell; a turbine in
which a combustion gas discharged from the combustor expands and
the pressure of the combustion gas drops to a negative pressure; a
compressor for compressing an exhaust gas discharged from the
turbine to increase the pressure of the exhaust gas; and a heat
exchanger for transferring heat from the high-temperature exhaust
gas discharged from the turbine to low-temperature air to be
supplied to the fuel cell. The term "atmospheric pressure"
signifies the pressure of the environment in which the system is
installed and the term "negative pressure" signifies a pressure
lower than the atmospheric pressure.
Fuel and air interact through an electrolyte in the fuel cell to
generate power and the fuel cell discharges a high-temperature cell
exhaust gas. The combustor burns the high-temperature cell exhaust
gas and discharges a combustion gas. The turbine is driven by the
combustion gas of a pressure approximately equal to the atmospheric
pressure. The combustion gas expands and the pressure of the
combustion gas drops to a negative pressure while the combustion
gas flows through the turbine. The compressor raises the pressure
of the exhaust gas discharged from the turbine. The expanded
exhaust gas discharged from the turbine. The heat exchanger
transfers the heat of the expanded exhaust gas discharged from the
turbine to low-temperature air to be supplied to the fuel cell.
Since the exhaust gas is supplied to the compressor after the
temperature of the exhaust gas has been thus decreased, the exhaust
gas can be compressed at a high compression efficiency and thereby
the efficiency of the gas turbine is improved. The air heated at a
high temperature by the heat of the exhaust gas discharged from the
turbine is supplied to the fuel cell to increase power generation
efficiency. The combination of the atmospheric-pressure,
high-temperature fuel cell and the atmospheric-pressure turbine
enables the effective use of the thermal energy of the
high-temperature cell exhaust gas discharged from the fuel cell,
does not produce any high pressures in the system, makes an
additional emergency protective device unnecessary, and enables the
use of lightweight, easy-to-process structural and piping materials
to reduces the cost.
Preferably, the exhaust gas discharged from the compressor is mixed
in the air to be supplied to the fuel cell. Particularly, when the
fuel cell is a molten carbonate fuel cell (MCFC), the exhaust gas
can be supplied to the fuel cell by a low-power blower or the like
instead of compressing and supplying the exhaust gas to the fuel
cell by a recycle blower. Therefore, the partial pressure of carbon
dioxide around the cathode can be easily increased and power
generation efficiency can be improved even under an operating
condition where cathodic reaction rate is low.
Preferably, a cooler is disposed below the heat exchanger to cool
an exhaust gas discharged from the heat exchanger. The respective
efficiencies of the compressor and the gas turbine can be improved
by supplying the exhaust gas discharged from the heat exchanger to
the compressor after cooling the exhaust gas by the cooler.
A preferred embodiment of the present invention includes a second
compressor disposed coaxially with the compressor serving as a
first compressor to compress the exhaust gas discharged from the
compressor, and a second cooler for cooling the exhaust gas to be
supplied to the second compressor. The respective operating
efficiencies of the compressors are increased and the efficiency of
the gas turbine is increased because the exhaust gas supplied to
the compressors is cooled. The coaxially disposed compressors have
one and the same shaft.
Another embodiment of the present invention includes an evaporator
capable of recovering heat from the exhaust gas discharged from the
turbine and generating steam by the recovered heat, and a reforming
device for reforming the fuel by using steam generated by the steam
generator and supplying the reformed fuel to the fuel cell. Thus
the fuel is reformed by the steam generated by the evaporator using
waste heat of the system. When the fuel is natural gas, natural gas
can be reformed to produce a fuel gas of high-quality having high
CO and H.sub.2 concentrations for fuel cells.
A third embodiment of the present invention is provided with an air
intake branch line through which part of air to be supplied to the
fuel cell flows. When air is supplied at an excessively high flow
rate to the fuel cell, part of the air is supplied through the air
intake branch line to the combustor. When air is supplied at an
excessively high flow rate higher than a flow rate suitable for
supplying air to the fuel cell to the heat exchanger disposed above
the fuel cell to cool the exhaust gas discharged from the turbine
satisfactorily, excessive air is carried by the air intake branch
line to the combustor and is used for burning the cell exhaust gas
discharged from the fuel cell in the combustor.
The fuel cell-atmospheric-pressure turbine hybrid system may be
provided with a fuel supply device for supplying a fuel other than
the cell exhaust gas. The combustion temperature of the cell
exhaust gas can be controlled by burning the fuel supplied by the
fuel supply device in the combustor to facilitate controlling the
output of the turbine.
A fourth embodiment of the present invention includes a second
turbine disposed coaxially with the turbine as a first turbine, a
second combustor disposed between the first and the second turbine
and capable of burning a fuel and an exhaust gas discharged from
the second turbine and of supplying a combustion gas to the first
turbine. The exhaust gas discharged from the first turbine is
supplied to the heat exchanger. The second combustor burns the
exhaust gas discharged from the second turbine and supplies the
high-temperature combustion gas to the first turbine. Consequently,
the output of the first turbine increases.
A fuel cell-atmospheric-pressure turbine hybrid system in a second
aspect of the present invention includes: a combustor for burning a
cell exhaust gas discharged from an atmospheric-pressure,
high-temperature fuel cell; a turbine in which a combustion gas of
a pressure substantially equal to the atmospheric pressure
discharged from the combustor expands and the pressure of the
combustion gas drops to a negative pressure; a compressor for
compressing an exhaust gas discharged from the turbine to increase
the pressure of the exhaust gas; and an air supply line through
which air is supplied to the combustor.
The fuel cell-atmospheric-pressure turbine hybrid system in the
second aspect of the present invention, similarly to the fuel
cell-atmospheric-pressure turbine hybrid system in the first aspect
of the present invention, includes the atmospheric-pressure,
high-temperature fuel cell and the atmospheric-pressure turbine in
combination. Therefore, the thermal energy of the high-temperature
cell exhaust gas discharged from the fuel cell can be effectively
used, any high pressures are not produced in the system, an
additional emergency protective device is unnecessary, and
lightweight, easy-to-process structural and piping materials can be
used to reduce the cost. Since the exhaust gas discharged from the
turbine is supplied to the fuel cell after the pressure of the
exhaust gas has been increased by the compressor, the thermal
energy of the exhaust gas can be effectively used by the fuel cell
without using a circulation blower or the like. The MCFC needs much
CO.sub.2 around the cathode. Since the exhaust gas has a high
CO.sub.2 concentration, the power generation efficiency of the fuel
cell increases. Oxygen can be supplied to the combustor at an
increased rate by supplying air through the air supply line into
the combustor. Consequently, the combustion efficiency of the
combustor can be increased.
Another embodiment of the present invention includes a heat
exchanger for transferring heat of an exhaust gas discharged from
the turbine to an exhaust gas discharged from the compressor. The
high-temperature exhaust gas discharged from the turbine and cooled
at a low temperature through heat exchange in the heat exchanger
and the low-temperature exhaust gas is supplied to the inlet of the
compressor. Thus the power for driving the compressor can be
decreased and the efficiency of the turbine can be increased. The
exhaust gas discharged from the compressor is heated at a high
temperature by the heat of the high-temperature exhaust gas
discharged from the turbine in the heat exchanger, and the
high-temperature exhaust gas is supplied to the fuel cell.
Consequently, the power generation efficiency of the fuel cell can
be further increased.
A preferred embodiment of the present invention includes an air
supply branch line branched from the air supply line to supply part
of air flowing through the air supply line to the fuel cell. Thus
the power generation efficiency of the fuel cell can be
increased.
Another embodiment of the present invention further includes an air
distribution valve placed at the joint of the air supply line and
the air supply branch line to adjust the distribution of air to the
air supply line and the air supply branch line. Thus air can be
properly supplied to the fuel cell according to the type and
capacity of the fuel cell to increase the efficiency of the fuel
cell. When the fuel cell is a solid oxide fuel cell (SOFC), the
cathode of the fuel cell does not need much carbon dioxide gas, but
needs much oxygen, Therefore, the air distribution valve is
operated so as to supply air at an increased flow rate to the fuel
cell. When the fuel cell is a MCFC, the cathode of the fuel cell
needs much carbon dioxide gas. Therefore, the air distribution
valve is operated to stop supplying air to the fuel cell or to
reduce the flow rate air flowing into the fuel cell so that the
carbon dioxide concentration of the exhaust gas compressed by the
compressor and supplied to the fuel cell increases.
As apparent from the foregoing description, the fuel
cell-atmospheric-pressure turbine hybrid system of the present
invention effectively uses the thermal energy of the cell exhaust
gas discharged from the atmospheric-pressure, high-temperature fuel
cell, does not need any emergency protective device, and enables
the use of lightweight, easy-to-process structural and piping
materials to reduces the cost.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a fuel cell-atmospheric turbine hybrid
system in a first embodiment according to the present
invention;
FIG. 2 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a second embodiment according to the
present invention;
FIG. 3 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a third embodiment according to the
present invention;
FIG. 4 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a fourth embodiment according to the
present invention;
FIG. 5 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a fifth embodiment according to the
present invention;
FIG. 6 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a sixth embodiment according to the
present invention;
FIG. 7 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a seventh embodiment according to the
present invention;
FIG. 8 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in an eighth embodiment according to the
present invention; and
FIG. 9 is a block diagram of a fuel cell-atmospheric-pressure
turbine hybrid system in a ninth embodiment according to the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be described
with reference to the accompanying drawings.
FIG. 1 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a first embodiment according to the present invention in a block
diagram. Referring to FIG. 1, the fuel cell-atmospheric-pressure
turbine hybrid system includes an atmospheric-pressure,
high-temperature fuel cell 1 and an atmospheric-pressure turbine
APT in combination. The atmospheric-pressure turbine APT uses a
cell exhaust gas G1 of a pressure substantially equal to the
atmospheric pressure discharged from the fuel cell 1 as a fuel. The
atmospheric-pressure turbine APT is provided with a combustor 2 for
burning the cell exhaust gas G1 discharged from the fuel cell 1, a
turbine 3 in which a combustion gas G2 discharged from the
combustor expands and the pressure of the combustion gas drops to a
negative pressure, a compressor 4 driven by the turbine 3 to
increase the pressure of an exhaust gas discharged from the turbine
3, and a heat exchanger 5 for transferring the heat of the
high-temperature exhaust gas G3 discharged from the turbine 3 to
environmental, low-temperature air A to be supplied to the fuel
cell 1. The atmospheric-pressure turbine APT is of a single-shaft
type. The turbine 3 and the compressor 4 has one and the same shaft
10 in common. The shaft 10 is connected to a generator 40, namely,
a load on the atmospheric-pressure turbine APT. The
atmospheric-pressure turbine APT may be of a dual shaft type
provided with first and second shafts, the turbine 3 and the
compressor 4 may be linked by the first shaft, and the turbine 3
and the generator 40 may be linked by the second shaft.
In the first embodiment shown in FIG. 1, the fuel cell 1 is a MCFC.
The fuel cell 1 has an anode 11, a cathode 12 and an electrolyte
layer 13 extending between the anode 11 and the cathode 12. Carbon
monoxide (CO) and hydrogen gas (H.sub.2) generated from the fuel F
of a normal pressure supplied to the anode 11 and air A of a normal
pressure supplied to the cathode 12 interact through the
electrolyte layer 13 to generate electric power. The fuel F is, for
example, natural gas.
The combustor 2 burns a normal-pressure, high-temperature cell
exhaust gas G1 containing unreacted gases and excess air and
discharged from the fuel cell 1 and discharges an exhaust gas G2.
The turbine 3 is driven by the exhaust gas G2 received from the
combustor 2. The turbine 3 drives the compressor 4 and the
generator 40. The combustion gas G2 expands and the pressure
thereof decreases to a negative pressure as the combustion gas S2
flows through the turbine 3 and becomes a negative-pressure,
intermediate-temperature exhaust gas G3. The heat exchanger 5
transfers the heat of the exhaust gas G3 to the low-temperature air
A to be supplied to the fuel cell 1. The exhaust gas G3 thus used
for heating the air A becomes a low-temperature exhaust gas G4. The
compressor 4 compresses the exhaust gas G4 at the atmospheric
pressure. Since the exhaust gas G4 has a low temperature, the
compressor 4 is able to compress the exhaust gas G4 efficiently,
which improves the efficiency of the atmospheric-pressure turbine
APT. The air A heated at a high temperature by the heat exchanger 5
is supplied to the cathode 12 of the fuel cell 1. Oxygen contained
in the air A serves as an oxidizer to promote the chemical
reactions of the components of the fuel F and, consequently, power
generating efficiency is increased. An exhaust gas G5 discharged
from the compressor 4 is supplied to the fuel cell 1 and is mixed
with the air A.
The fuel cell 1 is of an atmospheric-pressure, high-temperature
type and the atmospheric-pressure turbine APT is of an atmospheric
pressure type. Therefore, the atmospheric-pressure turbine APT is
able to use effectively the thermal energy of the high-temperature
cell exhaust gas G1 discharged from the fuel cell 1. Any high
pressures are not developed in the system, any emergency protective
device, which is indispensable to the conventional fuel
cell-turbine hybrid system, is not necessary. Therefore,
lightweight, easy-to-process structural and piping materials can be
used for constructing the fuel cell 1 and the
bathometric-temperature turbine APT and thereby the system can be
manufactured at a low cost.
The exhaust gas G5 discharged from the compressor 4 is mixed in the
air A to be supplied to the fuel cell 1. Therefore, the exhaust gas
G5 can be supplied to the atmospheric-pressure fuel cell by a
blower or the like requiring very low power, while the exhaust gas
G5 is supplied to a high-pressure fuel cell by a recycle blower in
the conventional hybrid system. Consequently, the partial pressure
of carbon dioxide around the cathode 12 can be easily increased and
power generation efficiency can be improved even under an operating
condition where cathodic reaction rate is low. The fuel cell 1 may
be a SOFC. When fuel cell 1 is a SOFC, the exhaust gas G5 is not
mixed in the air A and is discharged outside of the system.
FIG. 2 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a second embodiment according to the present invention.
Basically, the fuel cell-atmospheric-pressure turbine hybrid system
in the second embodiment is similar to the fuel
cell-atmospheric-pressure turbine hybrid system in the first
embodiment shown in FIG. 1. The fuel cell-atmospheric-pressure
turbine hybrid system shown in FIG. 2 includes, in addition to
components corresponding to those of the first embodiment, a spray
type cooling device 6. The cooling device 6 is disposed between the
compressor 4 and the heat exchanger 5. The cooling device 6 sprays
water on an exhaust gas G4 discharged from the heat exchanger 5 to
cool the exhaust gas G4. Then, a moistened exhaust gas G6 is
supplied to the compressor 4. The moisture contained in the exhaust
gas G6 evaporates in the compressor 4 and absorbs latent heat of
vaporization from the exhaust gas G6 to cool the exhaust gas G6 at
a low temperature. Consequently, the compressor compresses the
exhaust gas G6 at a high efficiency and the efficiency of the
atmospheric-pressure turbine APT is improved.
FIG. 3 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a third embodiment according to the present invention. The fuel
cell-atmospheric-pressure turbine hybrid system in the third
embodiment includes, in addition to components corresponding to
those of the fuel cell atmospheric-pressure turbine hybrid system
in the second embodiment, a second compressor 41 disposed coaxially
with the first compressor 4 corresponding to the compressor 4 of
the second embodiment and having a shaft 10 in common with the
first compressor 4, a first cooling device 6 corresponding to the
cooling device 6 of the second embodiment, a spray type second
cooling device 61 disposed between the first compressor 4 and the
second compressor 41 to cool an exhaust gas G7 discharged from the
first compressor 4. The second cooling device 61 sprays water on
the exhaust gas G7 discharged from the first compressor 4 to cool
the exhaust gas G7. Then, a moistened exhaust gas G8 is supplied to
the second compressor 41. The moisture contained in the exhaust gas
G8 evaporates in the second compressor 41 and absorbs latent heat
of vaporization from the exhaust gas G8 to cool the exhaust gas G8
at a low temperature. An exhaust gas G9 discharged from the second
compressor 41 is mixed in the air A, carbon dioxide that serves as
an oxygen-carrying medium in the fuel cell 1 is recovered and is
supplied to the cathode 12. Since the two cooling devices 6 and 61
cools the exhaust gases G6 and G8 flowing into the two compressors
4 and 41, respectively. Consequently, the compressors 4 and 41
compress the exhaust gases G6 and G8 at a high efficiency and the
efficiency of the atmospheric-pressure turbine APT is improved. The
spray type cooling devices 6 and 61 shown in FIGS. 2 and 3, namely,
direct type water sprayers, may be replaced with indirect type
cooling devices internally provided with cooling pipes.
FIG. 4 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a fourth embodiment according to the present invention. The fuel
cell-atmospheric-pressure turbine hybrid system in the fourth
embodiment includes, in addition to components corresponding to
those of the first embodiment shown in FIG. 1, an evaporator 7
connected to the outlet of the turbine 3 and a reforming device 8
connected to the evaporator 7. The evaporator 7 generates steam S
by heat recovered from the exhaust gas G3 discharged from the
turbine 3. The reforming device 8 decomposes the fuel F into CO and
H.sub.2 by using the steam S generated by the evaporator 7 and
supplies CO and H.sub.2 to the fuel cell 1. Thus the hybrid system
is able to reform the fuel F by using waste heat.
FIG. 5 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a fifth embodiment according to the present invention. The fuel
cell-atmospheric-pressure turbine hybrid system in the fifth
embodiment includes, in addition to components corresponding to
those of the first embodiment shown in FIG. 1, an air intake branch
line 9 through which part of the air A to be supplied to the fuel
cell 1 flows. When the air A is supplied at an excessively high
flow rate to the fuel cell 1, part of the air A is supplied through
the air intake branch line 9 directly to the combustor 2. When the
air A is supplied at an excessively high flow rate higher than a
flow rate suitable for supplying the air A to the fuel cell 1 to
the heat exchanger 5 disposed above the fuel cell 1 to cool the
exhaust gas G3 discharged from the turbine 3 satisfactorily,
excessive air A is carried by the air intake branch line 9 directly
to the combustor 2 and is used for burning the cell exhaust gas G1
discharged from the fuel cell 1 in the combustor 2.
FIG. 6 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a sixth embodiment according to the present invention. The fuel
cell-atmospheric-pressure turbine hybrid system in the sixth
embodiment includes, in addition to components corresponding to
those of the first embodiment, a fuel supply device 20, such as a
spray nozzle, for supplying a liquid or gaseous fuel F1 to the
combustor 3. The combustor 2 burns the fuel F1 supplied by the fuel
supply device 20 to control the combustion temperature of the cell
exhaust gas G1 dominating the temperature of the exhaust gas G2 to
be supplied to the turbine 3. The control of the temperature of the
exhaust gas G2 facilitates the control of the output of the turbine
3. For example, when the combustor 2 is unable to burn the cell
exhaust gas G1 at a sufficiently high temperature, the temperature
of the exhaust gas G3 to be supplied to the turbine 3 can be
increased by burning the fuel F1 supplied by the fuel supply device
20 to the combustor 2 and burning the fuel F1 in the combustor
2.
FIG. 7 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a seventh embodiment according to the present invention. The
fuel cell-atmospheric-pressure turbine hybrid system in the seventh
embodiment includes, in addition to components corresponding to
those of the third embodiment shown in FIG. 3, a first turbine 3
corresponding to the turbine 3 of the third embodiment, a second
turbine 31 disposed coaxially with the first turbine 3, and a
second combustor 21 to which a liquid or gaseous fuel F2 is
supplied. An exhaust gas G12 discharged from the first turbine 3 is
supplied to the heat exchanger 5. An exhaust gas G10 discharged
from the second turbine 31 is mixed in the fuel F2 and burned in
the second combustor 21, and a high-temperature exhaust gas G11 is
supplied to the first turbine 3. Consequently, the output of the
first turbine 3 increases.
FIG. 8 shows a fuel cell-atmospheric-pressure turbine hybrid system
in an eighth embodiment according to the present invention in a
block diagram. The fuel cell-atmospheric-pressure turbine hybrid
system in the eighth embodiment includes, similarly to the first
embodiment shown in FIG. 1, a combustor (reactor) 2, a turbine 3
and a compressor 4. The outlet of the compressor 4 is connected to
the cathode 12 of the fuel cell 1 by an exhaust gas line 50. An air
supply line 51 is connected to the combustor 2 to supply air A1
from the environment to the combustor 2.
The exhaust gas G3 discharged from the turbine 3 is compressed by
the compressor 4 to raise the pressure of the exhaust gas G3. An
exhaust gas G22 discharged from the compressor 4 is supplied
through the exhaust gas line 50 directly to the cathode 12 of the
fuel cell 1. Thus the thermal energy of the exhaust gas G22 can be
effectively used by the fuel cell 1 without using any circulating
blower or the like. If the fuel cell 1 is a MCFC, the cathode 12
needs a large quantity of CO.sub.2. Since the exhaust gas G22
supplied to the fuel cell 1 contains CO.sub.2, the power generation
efficiency of the fuel cell 1 is improved. The air A1 is supplied
through the air supply line 51 to the combustor 2. Consequently,
oxygen gas is supplied at an increased flow rate to the combustor
2, the efficiency of the reaction of the exhaust gas G1 discharged
from the fuel cell 1, namely, combustion efficiency, can be
increased.
This embodiment is provided with a fuel reforming device 52 for
reforming a fuel F to be supplied to the anode 11 of the fuel cell
1. The reforming device 52 is connected to the lower end of the
cathode 12 of the fuel cell 1 by an exhaust gas branch line 53.
Part G20 of the high-temperature exhaust gas G1 to be supplied from
the cathode 12 to the combustor 2 is supplied to the reforming
device 52 and is used for reforming the fuel F.
This embodiment is provided with an air preheater 54 for preheating
the air A1 that flows through the air supply line 51. The air
preheater 54 is connected to the fuel reforming device 52 by an
exhaust gas line 55 to preheat the air A1 by the heat of the
exhaust gas G21 discharged from the fuel reforming device 52
through heat exchange in the air preheater 54. Thus the preheated
air A1 is supplied through the air supply line 51 to the combustor
2. Consequently, the combustion efficiency of the combustor 2 is
further improved. If the fuel F is natural gas, the fuel gas F1 is
decomposed into CO and H.sub.2 by an exhaust gas G20 discharged
from the cathode 12, and CO and H.sub.2 are supplied to the fuel
cell 1.
An exhaust heat exchanger 56 makes an exhaust gas G5 discharged
from the compressor 4 and an exhaust gas G3 discharged from the
turbine 3 exchange heat. The temperature of the high-temperature
exhaust gas G3 discharged from the turbine 3 is decreased through
heat exchange in the heat exchanger 56. A spray type cooling device
57 is disposed between the exhaust heat exchanger 56 and the
compressor 4. An exhaust gas G4 is cooled by the cooling device 57
and the temperature thereof decreases. The low-temperature exhaust
gas G4 is supplied to the compressor 4. Consequently, power
necessary for driving the compressor 4 can be reduced. The exhaust
gas G5 discharged from the compressor 4 is heated by the heat of
the high-temperature exhaust gas G3 discharged from the turbine 3
in the exhaust heat exchanger 56. The high-temperature exhaust gas
G22 is supplied to the cathode 12 of the fuel cell 1, which further
increases the power generation efficiency of the fuel cell 1. Part
of the exhaust gas G22 being supplied from the exhaust heat
exchanger 56 to the cathode 12 may be sent to the fuel reforming
device 52 to use the thermal energy of the part of the exhaust gas
22 for reforming the fuel F.
The change of state of the exhaust gases discharged from the hybrid
system shown in FIG. 8 will be numerically explained. In the
following description, the unit of pressures P is bar, the unit of
temperatures T is .degree. C. and the unit of flow rates G is kg/h.
Cell output is 250 kW and plant output is 300 kW. The fuel (1.08P,
32.0T, 120G) is reformed by the fuel reforming device 52 and the
reformed fuel F is supplied to the anode 11 of the fuel cell 1 to
generate power by the fuel cell 1. The exhaust gas G1a discharged
from the anode 11 and the exhaust gas G1c discharged from the
cathode 12 are supplied to and burned by the combustor 2. The fuel
F supplied from the fuel reforming device 52 to the anode 11 has
106P, 580T and 120G, the exhaust gas G1a from the anode 11 has
1.05P, 650T and 620G, and the exhaust gas G1c from the cathode 12
has 1.05P, 650T and 2500G. The exhaust gases G1a and G1c
respectively from the anode 11 and the cathode 12 are supplied to
the combustor 2. Part of the exhaust gas G1c from the cathode 12 is
supplied through the exhaust gas branch line 53 to the fuel
reforming device 52 to use the thermal energy of the part of the
exhaust gas G1c for reforming the fuel F. The exhaust gas G1c
supplied to the combustor 2 has 1.04P, 650T and 1180G. The exhaust
gas 20 supplied to the fuel reforming device 52 has 1.04P, 650T and
1320G. The exhaust gas G3 supplied from the combustor 2 to the
turbine 3 has 0.99), 820T and 3000G. The exhaust gas G3 discharged
from the turbine 3 has 0.33P, 600T and 3000G. The exhaust gas G4
supplied from the exhaust heat exchanger 56 through the cooling
device 57 to the compressor 4 has 0.31P, 40.0T and 3000G. The
exhaust gas G22 discharged from the compressor 4, heated by the
exhaust heat exchanger 56 and supplied through the exhaust gas line
50 to the cathode 12 has 1.06P, 580T and 3000G.
The air A1 taken into the air preheater 54 has 1.01P, 25.0T and
1200G. The exhaust gas G21 passing through the fuel reforming
device 52 and heating the air A1 has 1.02P, 414T and 1414G. The
preheated air Al flowing through the air supply line 51 into the
combustor 2 has 1.00P, 400T and 1200G. The output power of the fuel
cell 1 is 250 kW, the power generation efficiency of the fuel cell
1 is 48.0% LHV. The output power of the hybrid system is 300 kW,
the power generation efficiency of the hybrid system is 57.6% LHV.
Thus a high-power, high-efficiency power generating system is
provided.
FIG. 9 shows a fuel cell-atmospheric-pressure turbine hybrid system
in a ninth embodiment according to the present invention. A fuel
cell 1 included in the fuel cell-atmospheric-pressure turbine
hybrid system in the ninth embodiment is a SOFC. The hybrid system
in the ninth embodiment includes, in addition to components
corresponding to those of the hybrid system in the eighth
embodiment, an air supply line 58 branching out from the air supply
line 51 and connected to the cathode 12 of the fuel cell 1. Part of
the air A1 is supplied through the air supply line 51 to the
cathode 12 of the fuel cell 1. An air distribution valve 59 is
placed at the joint of the air supply line 51 and 58 to adjust the
distribution of the air A1 to the air supply lines 51 and 58.
Part of the air A1 flowing through the air supply line 51 is
supplied through the air supply line 58 to the cathode 12 of the
fuel cell 1. The cathode 12 of the fuel cell 1, namely, the SOFC,
does not need much CO.sub.2, but needs much O.sub.2. Power
generation efficiency is increased by increasing the supply of
O.sub.2 to the cathode 12 of the fuel cell 1. The air distribution
valve 59 adjust the distribution of air to the fuel cell 1
according to the capacity of the fuel cell 1 to supply the air at a
proper flow rate to the fuel cell so that the efficiency of the
fuel cell 1 may be improved. Distribution of the air can be
adjusted according to the type of the fuel cell 1. For example,
when the fuel cell 1 is a MCFC requiring much CO.sub.2 for
efficient power generation, the air distribution valve 59 is
operated to stop or decrease the supply of the air A1 to the fuel
cell 1 so that the exhaust gas G22 compressed by the compressor 44
and flowing through the exhaust gas line 50 has a high CO.sub.2
concentration. When the fuel cell 1 is a SOFC, the air distribution
valve 59 is operated to increase the supply of the air A1 to the
fuel cell 1. The air distribution valve 59 is not necessarily
indispensable. For example, the respective flow rates of the air
flowing through a part, extending from the air distribution valve
59, of the air supply line 51 and the air flowing through the air
supply line 58 connected to the fuel cell 1 may be adjusted by
forming the part, extending from the air distribution valve 59, of
the air supply line 51 and the air supply line 58 by pipes of
different nominal diameters, respectively.
Although the turbine 3 and the compressor 4 are disposed coaxially
in each of the foregoing embodiments, the turbine 3 and the
compressor 4 do not necessarily need to be connected by the shaft;
the compressor 4 may be driven individually by a motor or the
like.
* * * * *